Critical Path Analysis – Revision Guide
CPA is a project analysis and planning technique that identifies the individual tasks of a project, places them in the correct sequence and allows for identification of the critical path
In order to construct a CPA, you need:
1. List of all the activities required to complete the project 2. The time (duration) that each activity will take to
3. The dependencies between the activities (e.g.: activity
D cannot be completed until activity B&C are done)
1. The earliest start time (EST) and latest finish time (LFT) that each activity can start and finish without making the project longer
Calculating the Earliest Start Time (EST)
• Work from Left to Right
• EST = EST of previous activity +
duration of previous activity
• If 2 activities lead into a node, then
use the HIGHEST value.
Calculating the Latest Finish Time (LFT)
• Work from Right to Left
• LFT = LFT at the end of following activity
– Duration of following activity
• If 2 activities lead into a node, then use
the LOWEST value.
2. Which activities are critical (i.e. on the longest path) and which have total float (i.e. can be delayed without making the project longer)
Tasks NOT on the Critical
Path CAN be delayed
and vice versa
Encourages forward planning
Based on assumptions, do you really know
how long each task will take? (Reliability of
More efficient use of resources
Does not guarantee the smooth running of
a project. Good operations and human
resource management is still required.
Can help with cash flow; capital and
labour is only paid for when it is needed.
Computer programs are needed for
massive or complex projects.
Reduces total time of a project
Easy to interpret, can help to simplify
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